Exposure to radon gas is associated with an increased risk for bronchogenic carcinoma in uranium miners and the discovery of high levels of radon in residential dwellings now raises the concern-that radon may increase the risk for bronchogenic carcinoma in the general population. While there have been recent investigations into the effects of radiation on transformation of various types of animals and human cells, very little information has been acquired regarding the effects of radiation on human bronchial epithelial cells. Recently, conditions for culturing normal human bronchial epithelial (NHBE) cells and immortalizing these cells with DNA viruses have been developed. These developments now allow in vitro evaluation of the genotoxic and tumorigenic effects of radon-simulated radiation on the target cell in radon-associated bronchogenic carcinogenesis. Such studies are of critical importance because there are important interspecies and intertissue differences in DNA repair and susceptibility to malignant transformation. We propose to irradiate 20 independent populations of the nontumorigenic human papillomavirus- immortalized human bronchial epithelial cell line BEP2D. The irradiated populations will be expanded and xenotransplanted into immunosuppressed athymic nude mice. Tumors that develop will be established as cell lines. The tumorigenic cell lines will be analyzed for new chromosomal deletions by cytogenetic and molecular genetic (restriction fragment length polymorphism (RFLP) and variable number of tandem repeat (VNTR) polymorphism) analysis. We will compare the chromosomal deletions that occur in common among these tumorigenic cell lines to those that occur in naturally occurring radon-associated bronchogenic carcinomas. This will allow determination of which genetic alterations play a role in the naturally occurring tumors. We will also evaluate the expression of p53 in the tumorigenic cell lines. If expression is altered, we will determine the genetic basis for the alteration. It is possible that cell lines tumorigenically transformed by radon alone will have a different mutational spectrum more specific to radon compared to naturally occurring tumors which usually are associated with co-exposure to other known carcinogens, including cigarette smoke and arsenic. The hypotheses we will be testing are l) that deletion of tumor suppressor genes plays an important role in high LET radon-simulated radiation associated tumorigenicity and 2) that the genetic alterations observed in the tumors we generate in vitro will be recognizable in naturally occurring radiation-associated bronchogenic carcinoma tissue. These studies have the following specific aims: l) Establish multiple independent tumorigenic transformants of the BEP2D cell line through exposure of independent cell populations to alpha radiation; 2) Identify chromosomal regions commonly deleted among the tumorigenic cell lines established in Aim l by cytogenetic and molecular genetic analysis; 3) Compare genetic lesions commonly deleted in the in vitro generated tumorigenic lines with those identified in primary bronchogenic carcinomas. In summary, through the proposed studies, we expect to identify specific genetic alterations responsible for radon-associated malignant transformation of human bronchial epithelial cells.